Look down the bay.

Do you see far away, under, the mountains, little islands, long and low?
Oh, yes.
Some of these are old slate, like the mountains; others are limestone; bits of the old coral-reef to the west of Ireland which became dry land.
I know.

You told me about it.
Then that land, which is all eaten up by the waves now, once joined Ireland to Cornwall, and to Spain, and to the Azores, and I suspect to the Cape of Good Hope, and what is stranger, to Labrador, on the coast of North America.
Oh! How can you know that?
Listen, and I will give you your first lesson in what I call Bio-geology.
What a long word! If you can find a shorter one I shall be very much obliged to you, for I hate long words.

But what it means is,--Telling how the land has changed in shape, by the plants and animals upon it.

And if you ever read (as you will) Mr.Wallace's new book on the Indian Archipelago, you will see what wonderful discoveries men may make about such questions if they will but use their common sense.